I've partially recreated your Simulink model, and it looks quite similar to the Classical Sliding Mode Control System. The "simulation hits (1000) consecutive zero crossings" error occurs due to a built-in feature that identifies rapid zero crossings and ends the simulation. In your case, this is triggered by the discontinuous action from the Sign block, causing frequent state switches.
If you're confident in the correctness of the model, you can disable this detection feature by unchecking "Enable zero-crossing detection" in the "Block parameters menu" of the Sign block.